The self calibrating emissivity and/or transmissivity independent multiwavelength pyrometer is ideally suited to measure the temperature of a surface when the emissivity of the surface and the transmissivity of the medium separating the surface from the pyrometer are either or both not known. Such is the case of the tungsten filament in a quartz lamp. Using a one-color pyrometer would require knowing the quartz lamp envelope transmissivity and the filament's emissivity to measure temperature. This information can only be obtained if samples of the filament and envelope are available. Assuming that these quantities are wavelength independent over a wavelength region, a ratioing 2-color pyrometer can measure the temperature, but the ratio signal is susceptible to noise. The disappearing filament pyrometer measures only a brightness temperature. It still needs the emissivity and transmissivity to make corrections to the measured temperature. The NASA self calibrating multiwavelength pyrometer is a recent addition to the list of pyrometers used in research and development. Its principle of operation makes it ideally suited to measure the temperature of surfaces without needing to know the emissivity of the surface, the transmissivity of the intervening medium or the calibration constant of the detector before hand. It has successfully measured the surface temperatures of tungsten, silicon carbide and refractory oxides in three infrared light sources. The measured temperatures are used to analyze the heat transfer in each case.